The aim of this section is to rule out case (2) of Theorem REF . The
proof strategy for doing so is as follows. By using [1]}, [2]}
and [3]} we determine the structure of \(X_{B}^{^}\) . From
this we derive an upper bound for \(\left|X_{B}\right|_{p}\) . Then,
we show that such a bound is in contrast with the lower bound for \(\left|X_{B}\right|_{p}\)  determined in Corollary REF , and
hence no cases arise.
